Aseptic package with steam permeable seal



ASEZPTIC PACKAGE WITH STEAM PERMEABLE SEAL Filed Aug; 19, 1949 INVENTORfia/Pm/v 0. 4/0 44 ATTO R N EY Patented Feb. 3, 1953 UNITED STATESPATENT OFFICE ASEPTIC PACKAGE WITH STEAM PERMEABLE SEAL Burton D.Morgan, Fords, N. J., assignor to Johnson & Johnson, a corporation ofNew Jersey 5 Claims.

This invention is directed to package unitsthat can be sterilized underheat so as to minimize danger of distortion or rupture duringsterilization thereof. In one of its more specific aspects the inventionis directed to novel methods and processes for sterilizing aseptic unitssuch as surgical dressings under heat, steam and pressure.

In the art of handling aseptic materials and especially surgicaldressings it has been found necessary to employ sealed envelope-typecontainers therefor to maintain the aseptic materials in proper physicaland sterile condition. These containers are generally throw-awaycontainers ordinarily composed of a material of sufficient density toprevent passage of microorganisms such as bacteria, but of sufiicientsteam permeability, particularly at elevated temperatures, to permitpenetration of steam into the container under conditions of steamsterilization. Paper is preferred, particularly sulfite Wrapper stock orglassine, either having a basic weight of from about fifteen to aboutforty pounds per ream of five hundred sheets measuring twenty-four bythirty-six inches and of a thickness of from about one to about fourmils.

Containers of this type may be manufactured readily, dressings and othermaterials may be inserted therein with ease, and the containers may besealed at high production speeds in any of the several manners known inthe art. The main disadvantage under production conditions of suchcontainers, is the weakness of their walls which are relatively thin andmay be torn readily.

Particularly is this true as the sealed containers are placed insterilizing chambers and heated to temperatures in the range of fromabout two hundred twenty to about two hundred sixty degrees Fahrenheit.The containers become distorted and rupture at times because the pressure exerted at said elevated temperatures by the air in the sealedcontainers is frequently much greater than the pressure in the chamberssurrounding the container particularly if vacuum is used in the processas is usual. Elevated ternperatures of the above indicated range arenecessary and usual for satisfactory steam sterilization. The adhesivecoatings necessary to bond the container walls for secure sealing of thecontainers due to their imperviousness add to the impermeability of thecontainers and in addition to increasing the tendency of the containersto burst, in some cases also decrease the steam penetration to a pointwhere poor sterilization occurs.

It is an object of this invention to provide a container for packagingsecurely aseptic materials. Further objects of the invention are theprovision of methods and containers for enclosing surgical dressings andthe like wherein bursting under conditions of heat sterilization isminimized, and which are adapted to speedy and economical productionmethods.

Still further objects will be apparent from the following description ofthe invention which provides a container enclosing the aseptic materialand having walls of sufiicient density to prevent passage ofmicroorganisms such as bacteria, but of suflicient permeability,particularly at elevated temperatures, to permit penetration of steaminto the container under sterilizing conditions, the insides of whichwalls are coated by a layer of discrete dots of heat sealing material.It is surprising to note that containers of this type may be sealedsecurely so as to prevent contamination after sterilization but retainsufficient porosity to permit passage of air from the container as theair within expands with rising temperature, thus preventing rupture ofthe container as sterilization proceeds.

Further details of the invention will be readily apparent from thefollowing description and drawing wherein:

Fig. 1 is a plan view of a container holding an adhesive bandage withthe top wall partially removed and illustrates the type of package thatmay be sterilized by practicing the present invention;

Fig. 2 is a vertical section through line 2-2 of g- Fig. 3 is a planview of one of the two walls of the container illustrating a typicalpattern of the adhesive coating on the container wall.

The drawing illustrates one example of a product that may be sterilizedreadily in accordance with this invention and in this instance, there isprovided a container comprising a bottom wall 5! and a top wall l2.Between these two walls, a dressing or other aseptic material such as anadhesive bandage it is positioned. One of the walls or both may becoated with an adhesive coating 13 which is applied in the form ofminute, discrete dots I4, e. g. in the form of rotogravure printing andby a rotogravure printing process. The exact sires of the individualdots of the coating and the intervals between these dots may be variedbut it is noted for best results, particularly with papers of theglassine or sulfite wrapper stock type, the intervals between dots arepreferably in the range of from about one tenth to about four ttnths ofa millimeter and the diameters of the dots are preferably in the rangeof from about two-tenths to about seven-tenths of a millimeter. Inpreferred embodiments of the invention the combined areas of the dotsamount to from about twenty to about fifty per cent of the total areawherein the coating is applied. The adhesive coating may be anyconventional heat sealing adhesive coating, preferably one that isnontacky at normal room temperatures, but those adhesive coatings thatare based on vinyl halide copolymers, vinyl ester and ether polymers andcellulose esters and ethers are preferred.

The container walls H and I2 are sealed after insertion of the asepticarticle at marginal portions I5-l8 so as to enclose the articlecompletely. After this sealing steam sterilization may be resorted to inthe usual manner, substantially without bursting of containers. Aftersterilization the containers continue to enclose the aseptic materialssecurely and prevent access of bacteria and other microorganismsthereto.

In preferred embodiments the margins I5- l3 of the container around theaseptic unit In may be embossed as illustrated in Figs. 1 and 2 duringor before sealing so as to insure better contact for the adhesive withboth container walls at these sections. i

In order to illustrate the invention in even more detail and to simplifyits understanding but I not to limit its scope two specific embodimentsof the invention follow:

Example I Two mil white sulfite wrapper stock having a basis weight oftwenty-six pounds is coated with an adhesive composition of thefollowing formula:

Vinyl chloride acetate copolymer (ball and ring methochsoftening point266 F.)

87% vinyl chloride "1f 50 13% vinyl acetate Vinyl chloride acetateinterpolymers (ball and ring method, softening point 270 F.)

86% vinyl chloride 13% vinyl acetate "i 50 1% maleic acid The coating isarranged so as to produce heatsealing dots having average dimensions of0.475 millimeter, the average space between dots amounting to 0.300millimeter. The arrangement is systematic and fairly regular so thatthere are no dots varying fifty per cent in either of these dimensions.The surgical dressing is placed upon a strip made from the abovedescribed coated sheet in the manner shown in the drawing and a secondsimilarly coated strip is laid over the surgical dressing. The packageis then sealed as illustrated in Fig. 1. The product undergoessterilization without difficulty or rupture of the package and remainssterile throughout several months storage up to the point of use whenthe package is opened by the user.

Example I] and having a basis weight of twenty-five pounds and theadhesive has the formula:

Parts by weight Cellulose nitrate '70 Plasticizer 30 The preferredcellulose nitrate has a viscosity of 50 centipoises resulting in asolution comprising 12.2 per cent cellulose nitrate, 22 per cent ethylalcohol, 17.5 per cent ethyl acetate, and 48.3 per cent toluene. Anyplasticizer for cellulose nitrate (although tricresyl phosphate ispreferred in this particular formula) may be used.

In this case the dots of the coating have average diameters of 0.520millimeter and the average space between dots is approximately 0.350millimeter.

No difiiculties were experienced during sterilization and containersformed appeared to be well stabilized and retained their stability forsome time.

It is, of course, realized that wide variations may be made within thebroad concepts stated earlier and satisfactory results are obtained ifthe examples are varied in accordance with the spirit of the invention.The development has proven of great economy in the manufacture,sterilization, storage, sale, and use of surgical dressings and providesa sterile sealed surgical dressing at very low cost and with assuranceof sterility.

Many other variation of the invention illustrated and described hereinwill be apparent to those skilled in the art and are included in theinventive concept.

What is claimed is: V

1. An aseptic package comprising two sheet portions of material ofsufficient density to prevent passage of microorganisms but ofsufiicient steam permeability to permit passage of steam under heatsterilizing conditions, said sheet portions being disposed inface-to-face contacting relation and sealed to each other around theentire edge of said package to prevent entry of microorganisms into saidpackage, aseptic material enclosed between said sheet portions near thecenter of said package, a substantial part of said edge seal beingformed by densely spaced discrete dots of heat-sealing adhesive materialjoining together said edge portions of said sheet material to permitescape of gases from within said package during steam sterilizationwithout rupture of said sheets.

2. A substantially flat aseptic package comprising two sheet portions ofmaterial of sufficient density to prevent passage of microorganisms butof sufficient steam permeability to permit passage of steam under heatsterilizing conditions, said sheet portions being disposed infaceto-face contacting relation and sealed to each other around theentire edge of said package to prevent entry of microorganisms into saidpackage, aseptic material enclosed between said sheet portions near thecenter of said package, a major part of said edge seal being formed bydensely, regularly spaced discrete dots of heat-sealing adhesivematerial joining together said edge portions of said sheet material topermit escape of gases from within said package during steamsterilization without rupture of said sheets.

3. A substantially fiat aseptic package comprising two sheets ofmaterial of sufiicient density to prevent passage of microorganisms butof sumcient steam permeability to permit passage of steam under heatsterilizing conditions, said sheets being disposed in face-to-facecontacting relation and sealed to each other around the entire edge ofsaid package to prevent entry of microorganisms into said package,aseptic material enclosed between said sheets near the center of saidpackage, said edge seal being formed throughout by densely, regularlyspaced discrete dots of heat-sealing adhesive material, non-tacky atnormal room temperature, joining together said edge portions of saidsheet material to permit escape of gases from within said package duringsteam sterilization without rupture of said sheets.

4. A substantially flat aseptic package co..- prising two sheets ofwhite sulfite wrapper paper stock of sufficient density to preventpassage of microorganisms but of sufiicient steam permeability to permitpassage of steam under heat sterilizing conditions, said sheets beingdisposed in face-to-face contacting relation and sealed to each otheraround the entire edge of said package to prevent entry ofmicroorganisms into said package, aseptic material enclosed between saidsheets near the center of said package, said edge seal being formedthroughout by densely, regularly spaced discrete dots of heat-sealingadhesive material, non-tacky at normal room temperature, joiningtogether said edge portions of said sheet material to permit escape ofgases from within said package during steam sterilization withoutrupture of said sheets, said dots occupying from about twenty to aboutfifty per cent of the sealed area of said edge.

5. A substantially flat aseptic package comprising two sheet portions ofglassine paper of suflicient density to prevent passage ofmicroorganisms but of sufficient steam permeability to permit passage ofsteam under heat sterilizing conditions, said sheet portions beingdisposed in faee-to-face contacting relation and sealed to each otheraround the entire edge of said package to prevent entry ofmicroorganisms into said package, aseptic material enclosed between saidsheet portions near the center of said package, a major part of saidedge seal being formed by densely, regularly spaced discrete dots ofheatsealing adhesive material joining together said edge portions ofsaid sheet material to permit escape of gases from within said packageduring steam sterilization without rupture of said sheets.

BURTON D. MORGAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,387,839 Davis Aug. 16, 19211,992,215 Kellet Feb. 26, 1935 2,249,424 Hanington July 15, 19412,256,024 Hill Sept. 16, 1941 2,291,149 Connor July 28, 1942 2,335,159Salfisberg Nov. 23, 1943 2,361,344 Yates Oct. 24, 1944 2,391,094 KargDec. 18, 1945 2,475,241 Hermanson July 5, 1949 2,476,740 Krall July 19,1949 FOREIGN PATENTS Number Country Date 430,067 Great Britain June 12,1935

